linux-kernel - RE: [PATCH v2 1/4] tools/nolibc: sys.h: add __syscall() and _

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Date:   Thu, 8 Jun 2023 14:35:49 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Zhangjin Wu' <falcon@...ylab.org>,
        "thomas@...ch.de" <thomas@...ch.de>, "w@....eu" <w@....eu>
CC:     "arnd@...db.de" <arnd@...db.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Thomas Weißschuh <linux@...ssschuh.net>
Subject: RE: [PATCH v2 1/4] tools/nolibc: sys.h: add __syscall() and
 __sysret() helpers

From: Zhangjin Wu
> Sent: 06 June 2023 09:10
> 
> most of the library routines share the same code model, let's add two
> helpers to simplify the coding and shrink the code lines too.
> 
...
> +/* Syscall return helper, set errno as -ret when ret < 0 */
> +static inline __attribute__((always_inline)) long __sysret(long ret)
> +{
> +	if (ret < 0) {
> +		SET_ERRNO(-ret);
> +		ret = -1;
> +	}
> +	return ret;
> +}

If that right?
I thought that that only the first few (1024?) negative values
got used as errno values.

Do all Linux architectures even use negatives for error?
I thought at least some used the carry flag.
(It is the historic method of indicating a system call failure.)

	David

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